A central goal of this research program is to describe the social and spatial environments in which older adults spend their time. We focus on the extent to which this activity space influences health trajectories. We theorize that the components of the person-environment relationship, including household, neighborhood, and network contexts, are interrelated and mutually constituted. We aim to 1) describe the activity space that older adults inhabit, and 2) explore the extent to which activity space, and the network, household, and neighborhood exposures related to it, affect short-term and pre-clinical changes in health. We will collect primary, multi-wave data from 600 Chicagoans aged 65 and older. We incorporate reports of network connectedness and activity tracking across physical space using GPS methodology. By equipping respondents with smart phones, we are able to collect real-time data on latitude, longitude and distance traveled. We use ecological momentary assessment (EMA) methodology to obtain respondents' reports of their social settings, health status, health behaviors, and well- being. In-person interviews will obtain self-reported and objective indices of health, including body mass index and a salivary measure to assess chronic stress exposure. A particularly innovative feature of this study is the ability to capture changes n quotidian symptoms, potentially indicative of chronic disease onset.